https://www.luogu.com.cn/record/143357696

#include<bits/stdc++.h>
using namespace std;
int top=-1,stk[109];
int main()
{
	int n,a;
	cin>>n>>a;
	while(n>0){
        top++;
        stk[top]=n%a;
        n/=a;
	}
	while(top>=0){
        if(stk[top]<10){
            cout<<stk[top];
            top--;
        }
        else{
            cout<<char(stk[top]-10+'A');
        }
	}
}

还有，蒟蒻没懂

cout<<char(stk[top]-10+'A');

的含义